It is important for an electric power system or a distribution system to properly control and manage the voltages in the whole electric power system even when the power flow changes due to fluctuations in the loads.
For example, Patent Literature 1 discloses a technology for accurately estimating true values of the system state by calculating estimate values of measurement errors and correction amounts of the system state by power flow calculation from measurement values of voltages, currents, etc. acquired by sensors arranged in the distribution system and the power flow calculation based on system configuration data.